6.1.1 - Cellular Control Flashcards
What is a mutation ?
A mutation is a change in the sequence of bases in DNA
What are the possible causes of changes in the DNA sequence ?
- Insertion - an extra nucleotide is added
- Deletion - a nucleotide is removed
- Substitution
What are the three types of substitution ?
- Nonsense
- Mis-sense
- Silent mutation
What is a nonsense substitution ?
The mutation results in one of the 3 stop codons (TAC, TAT, TGA)
What is a mis-sense substitution ?
Results in a different amino acid sequence being coded for
What is a silent mutation ?
Although it is a different codon, the same amino acid is coded for
What is a point mutation ?
Mutation that occurs because a single nucleotide is changed, added or removed
How can the primary structure be changed due to a mutation ?
- A new codon is formed because of the mutation
- This causes a different amino acid to be coded for
- The different amino acid can cause a change in the primary structure
What is the DNA code said to be ?
- Degenerate
- Non-overlapping
- Universal
How is the DNA code degenerate ?
Lots of different codons code for the same amino acid
How is the DNA code universal ?
The same codon codes for the same amino acid in all organisms
How is the DNA code non-overlapping ?
Each codon is read once, it does not overlap
What is a frameshift mutation ?
The insertion or deletion of a nucleotide or many nucleotides
What can a frameshift mutation lead to ?
- It can lead to the reading frame of the sequence of bases to be moved.
- This will change every successive codon from the point of mutation
What are the three effects of mutations ?
- Neutral effect
- Damaging effect
- Beneficial effect
How can a mutation be neutral ?
- Normal functioning proteins still synthesised
- Phenotype unchanged
How can a mutation be harmful ?
- Proteins not synthesised or are non functional
- Phenotype is negatively impacted
How can a mutation be beneficial ?
Proteins synthesised with a new and useful characteristic in the phenotype
What are the causes of mutations ?
- They can be spontaneous, often during DNA replication
- Rate of mutation can be increased by mutagens
What is a mutagen ?
A chemical, physical or biological agent which causes mutations
Give an example of a physical mutagen
Ionising radiations such as X - Rays
How do ionising radiations have an effect ?
- Break one or both DNA strands
- These breaks can be fixed but mutations can occur along the way
Give an example of a chemical mutagen
Deaminating agents
How does a deaminating agent have an effect ?
Chemically alter bases in DNA such as converting C to U in DNA, changing the base sequence
Give an example of a biological agent
Viruses
How do viruses have an effect ?
Viral DNA may insert itself into a genome, changing the base sequence
What effect can chromosome mutations have ?
- Deletion
- Duplication
- Translocation
- Inversion
What is deletion ?
A section of chromosome breaks off and is lost within the cell
What is duplication ?
Sections get duplicated on a chromosome
What is translocation ?
A section of one chromosome breaks off and joins another non homologous chromosome
What is inversion ?
A section of chromosome breaks off, is reversed, and then joins back onto the chromosome
What are the different ways in which genes can be regulated ?
- Transcriptional
- Post-transcriptional
- Translational
- Post-translation
What is transcriptional regulation ?
Genes can be turned on and off
What is post-transcriptional regulation ?
mRNA can be modified which regulates translation and the types of proteins produced
What is translational regulation ?
Translation can be stopped or started
What is a post-translational regulation ?
Proteins can be modified after synthesis which changes their functions
What are the different mechanisms that can affect the transcription of genes ?
- Histone modification
- Lac operon
- Chromatin remodelling
- Role of Cyclic AMP
What is heterochromatin ?
Tightly wound DNA causing chromosomes to be visible during cell division
What is euchromatin ?
Loosely wound DNA present during interphase
Why is the transcription of genes not able to happen with heterochromatin ?
RNA Polymerase cannot access the genes so transcription can not occur